Obesity among teenagers is epidemic. It is a leading preventable cause of death worldwide, with increasing prevalence in adults and children, and authorities view it as one of the most serious public health problems of the 21st century. For reasons no one actually knows, obesity was rare before the 20th century.
One problem in obesity is that insulin resistance increases and insulin levels rise, leading to diabetes.
What role does vitamin D play in the obese person’s tendency to get diabetes? That is, would a randomized controlled trial show that vitamin D decreased insulin resistance or decreased insulin levels? Insulin resistance is bad, the higher it is, the higher the insulin and the more insulin is required to get glucose into cells.
Doctor Anthony Belenchia and colleagues of the University of Missouri School of Medicine recently conducted a randomized placebo controlled trial of 4,000 IU/day in 35 morbidly obese teenagers (mean age 14), giving 21 children 4,000 IU/day of vitamin D and 23 placebo for six months. The average BMI was incredible at 39, making these kids morbidly obese.
The authors found the following:
- With 4,000 IU/day, vitamin D levels went from 19 ng/ml to 38 ng/ml, with 7% of the treatment group still having levels less than 30 ng/ml after six months.
- Fasting plasma glucose fell from 89.7 to 84.1 in the treatment group but were essentially unchanged in the placebo group, just missing significance (p=.08).
- Fasting plasma insulin fell in the treatment group but went up in the placebo group (p= .026).
- Calculated insulin resistance, as measured by two different markers, fell in the treatment group but increased in the placebo group (p= 0.033) and (p= 0.016)
- Leptin (a hormone that regulates appetite and hunger and that is elevated in obesity) fell from 43.5 to 36.7 while it increased in the placebo group (p= 0.028).
- Adiponectin (a hormone that is decreased in the obese) was not different between groups.
- However, the leptin/adiponectim ratio was significantly better in the 21 children in the treatment group (p= 0.045).
- BMI and markers of inflammation were not significantly different between treatment groups.
The authors concluded:
“In summary, the results from this investigation provide compelling support for routinely monitoring the vitamin D status of obese adolescents. The correction of poor vitamin D status through dietary supplementation may be an effective addition to the standard treatment of obesity and its associated insulin resistance.”
This was a great study. In the future someone should replicate it, but by treating for a year instead of six months and by using higher doses of vitamin D, enough to obtain natural 25(OH)D levels (around 50 ng/ml).
In this study, mean levels after 6 month of 4,000 IU/day were only 38 ng/ml, with 7% of the treated kids still having levels less than 30 ng/ml, although this may have been due to noncompliance. If vitamin D reduces serum leptin levels, and this study showed it did, then eventually vitamin D should reduce body weight, as lower leptin should decrease hunger and appetite. I suspect a longer study with a higher dose would find a mild diet pill like effect with vitamin D.
Lastly, obese or not, I think all teenagers are at risk of vitamin D deficiency, as so many of them are in school all day and in front of the computer and TV on weekends.